A motor vehicle is equipped with headlamps intended to produce a light beam that illuminates the road in front of the vehicle, in particular at night or in the case of low light levels.
Luminous modules of this type are already known. Such luminous modules are able to produce an illuminating light beam, for example a high beam, divided, vertically and horizontally, into luminous segments and at least certain luminous segments of which may be selectively turned off. This for example allows the road to be illuminated optimally while avoiding subjecting road users to glare.
Such luminous modules generate segmented light beams, which are known as pixel beams. It is for example possible to divide the overall light beam into a matrix array of luminous segments.
Generally, the vertical resolution of the light beam, i.e. the number of light segments in the vertical planes of the beam emitted by a headlamp, remains quite low. Thus, turning off one luminous segment plunges into darkness a segment of road that is often much larger than required to prevent a road user from being subjected to glare. It would be advantageous to be able to increase the vertical resolution of the light beam in order to be able to illuminate the road up to a road user located in front of the vehicle, while turning off luminous segments liable to subject the road user to glare.
These headlamps are preferably designed to illuminate a large lateral visual field but known lighting systems have a visibility that vehicle drivers sometimes find unsatisfactory. In particular, it is difficult, or even impossible, to ensure a large field of illumination in the horizontal plane of the path of the vehicle and to simultaneously ensure a high resolution in the vertical direction, for any angle in the horizontal plane. In addition, it is important to decrease the size of the projecting lenses, which should preferably have a diameter smaller than 80 mm, while using commercially available arrays of light-emitting diodes that each have a minimum size of 0.75 mm×0.75 mm. Moreover, for reasons of visual comfort, and for regulatory reasons, it is preferable for two adjacent segments in the horizontal plane to adjoin so that the overall light beam illuminates the road uniformly. However, known solutions do not allow a high vertical resolution to be obtained at the same time as a large horizontal field containing adjoining luminous segments, in particular when the light sources are too far apart from one another.
A known motor-vehicle headlamp lighting system, described in document US 2014/0307459 A1, comprises a primary optical module comprising a plurality of light sources, for example light-emitting diodes, each associated with respective light guides. A projecting secondary optical element, for example a lens, is associated with the primary optical module. This projecting secondary optical element may have a plurality of focal lengths. Such a lighting system nevertheless has certain drawbacks. Firstly, such a primary optical module, comprising a plurality of independent light guides each associated with one light source, is complex and expensive to produce. Thus, the focal lengths are chosen to coincide with the exit surfaces of the primary optic. Thus, this system requires the primary optic to be positioned at an angle relative to the optical axis of the projecting element, this making aligning and assembling the optical system complex and therefore expensive. The major drawback of such a system is that it is not possible to achieve vertical resolutions higher than 0.6° if standard commercially available light sources and projecting lenses having a large diameter, typically larger than 100 mm, are used.
Another lighting system, described in document DE102008013603, relates to an optical module comprising a matrix array of light emitters and allows a uniform light beam to be projected. The system comprises a matrix array of optical elements, each of funnel shape. Each optical element of the matrix array is positioned facing an emitter and its reflective interior surface ensures that a substantially parallel beam is projected towards the projector. Such a matrix array of conical reflective elements is expensive to manufacture. Furthermore, as with the projecting module described in document US 2014/0307459 A1, the system described in document DE102008013603 does not allow a high vertical resolution associated with a large horizontal projection angle to be obtained.
In another embodiment, described in document US2015131305A a strip of light sources is adapted to an integrally formed optical structure comprising a single light guide connected to a correcting optical portion. The bifocal secondary optic, ensuring the projection of light into the far optical field, has a vertical focal plane that coincides with the exit surface of the optical guide, this of course resulting in a poor resolution in the vertical direction.